POS0926 OPTICAL SPECTRAL TRANSMISSION IN THE DIAGNOSIS OF HAND OSTEOARTHRITIS: CLINICAL ASSOCIATIONS AND EVALUATION OF A NEW DIAGNOSTIC ALGORITHM INCLUDING ALL FINGER JOINTS
Authors: K. Triantafyllias, K. Altamimi, S. Gauch, A. Schwarting
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Optical spectral transmission (OST) is a modern diagnostic technology able to quantify joint inflammation in a non-invasive, rapid and examiner-independent manner [1-3]. The vast majority of studies on OST have been performed in patients with rheumatoid arthritis (RA) [1-3]. No sufficient data on the diagnostic value of OST regarding other arthropathies have been published. However, our study group and others could show that concomitant to RA joint pathologies, such as primary or secondary (post-arthritic) osteoarthritis (OA) could have an influencing effect on OST results [1,4]. <h3>Objectives</h3> Aim of this study was therefore to investigate the performance of OST in the diagnosis of OA and to evaluate its ability to identify activated OA changes. <h3>Methods</h3> Patients from two large Rheumatology departments with diagnosed finger and/or wrist OA and without any inflammatory joint disease, as well as healthy controls, were recruited in the context of this study. All study subjects were evaluated via clinical (counts of tender and swollen joints) and OST examinations. Moreover, OA-patients underwent laboratory (C-reactive protein, erythrocyte sedimentation rate) and X-ray examinations of both hands and the extent of osteoarthritic changes was evaluated by an established radiographic score [Kellgren-Lawrence (KL) score]. To evaluate OA activity, joint ultrasound (US) examinations [Grey-scale (GSUS), power Doppler (PDUS) scores] were performed in a subset of patients. Moreover, a new diagnostic algorithm including the distal interphalangeal joints (DIP) was examined next to the established algorithm concerning only wrists, MCP and PIP joints. <h3>Results</h3> <i>2,134</i> joints of OA patients [n=97; 80.4%♀; 68 years (58-76, IQR)] and <i>2,200</i> joints of healthy controls [n=100; 80%♀; 49 years (33.5-56, IQR)] were examined via OST. OA patients showed statistically significantly higher OST scores compared to control subjects [13.73 (11.19-16.51, IQR) vs. 10.19 (8.05-14.31, IQR); p&lt;0.001] during the evaluation of the algorithm including wrist, MCP and PIP joints. This difference remained significant also after adjusting for age and sex (p=0.033). The novel diagnostic algorithm including additionally DIP joints (next to MCP, PIP and wrists) showed also a statistically significant difference between patients and controls (p&lt;0.001, after adjustment p=0.021). Interestingly, receiver operating characteristics revealed an improved diagnostic performance when including DIP joints in the algorithm [Area under the curve (AUC) 0.718; 95%CI (0.645-0.792) (with DIP) vs AUC 0.698; 95%CI (0.625-0.771) (without DIP)]. OST did not correlate with GSUS/PDUS or KL-Score (all; p&gt;0.05). However, it did correlate moderately-significantly with patient hand-size (without DIPs: rho=0.337; p&lt;0.001; with DIPs: rho=0.363; p&lt; 0.001). <h3>Conclusion</h3> Hereby we could show that presence of OA can indeed influence OST values and that OA changes should be taken into account when interpreting OST results. Moreover, we found that inclusion of DIP joints can lead to an improvement of diagnostic performance of OST. To our knowledge, this the largest study examining the diagnostic value of OST in OA and the first external exploration of this specific DIP-associated algorithm. Value of OST in the follow up examinations of OA patients should be investigated in studies with longitudinal design. <h3>References</h3> [1]Triantafyllias K, et al. J Rheumatol. 2020;47(9):1314-1322 [2]Verhoeven MMA, et al. Arthritis Care Res. 2022;74(9):1493-1499 [3]Van Onna M, et al. Ann Rheum Dis. 2016;75(3):511-8 [4]Besselink NJ PLoS One. 2019; 14(2):e0209761 <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> Konstantinos Triantafyllias Speakers bureau: Pfizer, Novartis, Galapagos, Janssen, Chugai, Sanofi, AbbVie, Khalid Altamimi: None declared, Svea Gauch: None declared, Andreas Schwarting Speakers bureau: GSK, Novartis, Grant/research support from: GSK, Pfizer, AbbVie, Novartis, Roche